1. Field of the Invention
The present invention generally relates to a high pressure piston sealing system. More specifically, the present invention relates to a sealing system adapted for rigorous marine applications which prevent or inhibit the use of a seal lubricant.
2. Description of the Prior Art
In a variety of applications incorporating the use of a piston or similar reciprocating member, it is necessary to establish a dynamic seal between the moving or reciprocating member and the stationary element to prevent the flow of gases or fluids therebetween. This need is particularly accentuated in applications where high pressures or high temperatures, e.g., rigorous conditions, are involved.
To establish such a seal, a variety of designs have evolved, such designs generally incorporating the use of an O-ring placed about the outer periphery of the reciprocating element. The use of an O-ring in rigorous, high speed applications, however, presents a number of disadvantages. In such applications, the seal is subjected to a variety of stresses as determined by such varying parameters as differential pressure, precompression of the O-ring, material and hardness of the O-ring, roughness of the bore in which the O-ring operates, relative speed by which the O-ring moves through the bore, and degradation factors via chemical agents, etc. Further, if the O-ring or similar elastic element is to function favorably, the clearance between the reciprocating elements must be reduced. This low tolerance between the reciprocating members in conjunction with one or more of the above mentioned factors) places the O-ring or elastic seal under considerable lateral friction, often causing the seal to "roll up" or tear.
To overcome this problem, a seal lubricant is often used, said lubricant applied to the interior of the bore, or to the O-ring itself. Such a lubricant, however, is not useful in applications where the sealing surface are exposured to the marine environment. In such cases, the lubricant will rapidly wash away in a few strokes of the reciprocating member.
A variety of seal designs have been developed to overcome the above referenced problems of tearing and rolling. In one design, the O-ring is disposed in a cavity or groove and fitted with a rigid cap ring over its contacting surface. Such a design is seen, for example, in U.S. Pat. No. 4,749,202. In other designs, especially those adapted for extreme high pressure applications, the combination O-ring and cap ring are laterally buttressed by the positioning of anti-extrusion rings. In such a design, the O-ring is protected both from direct frictional wear as well as from lateral forces common in applications involving a closely tolerenced reciprocating element.
Disadvantages with these designs include the special tooling necessary to position and remove the O-rings, buttressing or bearing rings and cap rings which have been positioned about the piston or other reciprocating element. The need for such tooling is especially non desirable when the sealing assembly must be quickly removed or replaced, e.g., on board a marine vessel.
A further disadvantage with such sealing systems includes the need to often machine the piston or other sealing element in multiple pieces so as to allow for the ready removal or replacement of the sealing elements. Some seal designs have also been developed to overcome this problem. However, these designs dictate the use of hot oils or other hot inert fluids to soften the sealing members so that they may be placed about the reciprocating element. This process is both time consuming and detrimentally effects the sealing properties of the elements.